1. Field of the Invention
The present invention relates particularly to a fixing apparatus which is usable in image forming apparatuses such as a copying apparatus and a printer apparatus in an electrophotographic system using a thermally melting developer and which fixes a developer to an output object.
2. Description of the Related Art
A fixing apparatus incorporated in an image forming apparatus using an electrophotographic process applies heat to a toner (developer) positioned on an output object, that is, a recording material to soften the toner, and applies pressure to the toner to fix the toner to the recording material. In recent years, induction heating has been broadly utilized as a heating system capable of reducing a time from when power supply is started until temperature reaches fixable temperature at which the toner softens, that is, heating time.
However, in the fixing apparatus using the induction heating, it is difficult to correctly detect the temperature of a heat roller (heating member) for fixing the toner to the recording material.
There have been many proposals in order to improve these respects.
For example, it has been described in Japanese Patent Application Laid-Open No. 2003-229242 that an apparatus (fixing apparatus) for heating a heating object member by the induction heating has an optical system and a mirror for guiding infrared rays radiated from a heating object member to infrared-ray detection means, and power to be supplied to heating means for heating the heating object member is controlled based on the detected infrared rays.
For example, it has been described in Jpn. Pat. Appln. KOKAI Publication No. 10-31390 that in a fixing apparatus for an electrophotographic apparatus having non-contact temperature detection means having self temperature detection means, the temperature of a heat roller is obtained from temperatures by a multidimensional equation using the self temperature detected by the self temperature detection means and the temperature in the vicinity of the heat roller detected by the non-contact temperature detection means.
For example, it has been proposed in U.S. Pat. No. 5,819,136 that in the fixing apparatus of the image forming apparatus, an air current is generated toward the fixing apparatus, and the temperature of the fixing apparatus is controlled based on the temperature detected using the non-contact temperature detection means disposed in a region where the air current passes.
However, even by the proposal of any of the above-described documents, it has been difficult to correctly detect the temperature of the heating member (heat roller) within a slight temperature management width.